I didn't get the details from Nigel as my pc has taken a dislike to him, but I did take the opportunity to whinge to someone in EH that people would not climb Silbury if they knew they were causing damage - and the fact they aren't aware is because EH fences and signs are crap.
They took this very well and said they would look at it and also consider sending information sheets to schools and colleges.
Confrontation at the site is probably unwise and this even includes taking photographs of people on the hill. Climbing the hill is a daily occurrence so it is best to ignore it and let EH deal with it.
VBB